Using Ruby's Net FTP to upload a stream of partial chunks

ftp.rb

# Simple extension of Net::FTP to allow uploading a stream instead of a file
# This allows for transferring of files between servers without downloading entire file first

# The code below is a modification of the storbinary method in Net::FTP
# https://github.com/ruby/ruby/blob/trunk/lib/net/ftp.rb#L686
# It goes without saying that the code may break at anytime and may or may not work with other
# features of Net::FTP such as using Resume.

require 'net/ftp'

class Net::FTP
  #
  # Puts the connection into binary (image) mode, issue a STOR command with the
  # given filename and yields to the passed in block with a 'writer' lambda
  # This lambda can be called with a given chunk to write to the file.
  #
  def putbinarystream(filename) # :yield: data
    raise 'block required' unless block_given?
    synchronize do
      with_binary(true) do
        conn = transfercmd("STOR #{filename}")
        writer = lambda { |chunk| conn.write(chunk) }
        yield(writer) if block_given?
        conn.close
        voidresp
      end
    end
  rescue Errno::EPIPE
    # EPIPE, in this case, means that the data connection was unexpectedly
    # terminated.  Rather than just raising EPIPE to the caller, check the
    # response on the control connection.  If getresp doesn't raise a more
    # appropriate exception, re-raise the original exception.
    getresp
    raise
  end
end


## SAMPLE USAGE: Transferring files between different FTP Hosts
ftp1 = Net::FTP('ftpserver1', 'user', 'password')
ftp2 = Net::FTP('ftpserver2', 'user', 'password')
ftp2.putbinarystream('file1') do |writer|
  ftp1.retrbinary('RETR file1') do |chunk|
    writer.call(chunk)
  end
end